1. Field of the Invention
The methods and systems of this invention relate to the prevention and treatment of heart failure by means of a leadless external or implantable device.
2. Description of the Background Art
Heart Failure (HF) currently affects over 5 million patients in the United States alone. This population has been steadily increasing due to overall demographic aging and, in particular, the effects of new life-prolonging treatments to patients with chronic cardiac conditions. HF is defined by the ACC/AHA Task Force as a complex clinical syndrome that impairs the ability of the ventricle to fill with or eject blood. HF generally results from one or more underlying factors including hypertension, diabetes, valvular disease, cardiomyopathy, coronary artery disease, or structural changes to the heart muscle. HF is characterized by reduced ventricular wall motion in systole and/or diastole, and low ejection fraction. As the heart becomes less able to pump a sufficient volume of blood to the system, patients develop symptoms of fluid retention, shortness of breath, and fatigue. Patients with cardiac disease or patients who experience cardiac problems, e.g., ischemic episodes, are highly likely to eventually develop HF. It will be beneficial to offer preventative treatment to these patients so that they might avoid or postpone becoming HF patients.
New medications developed to treat HF have been generally ineffective, and device-based solutions appear to offer significant promise for afflicted patients in both preventing heart failure initially and ameliorating the progression of heart failure. The following are descriptions of four device-based therapies to treat, prevent, and/or delay progression of HF.
First, there are several reports of using therapeutic ultrasound to increase cardiac contractility, reduce aortic pressure, cause coronary vasodilatation, or increase tissue perfusion (tissue sonication). These reports describe the application of continuous and pulsed ultrasound over a wide range of treatment durations, timing intervals, ultrasound frequencies, and ultrasound intensities. In isolated rat papillary muscle, Forester et al. demonstrated increased contractility with continuous wave ultrasound. They speculated that the increase in contractility was due to the thermal effects or mechanical tension effects of ultrasound energy on the sarcolemma (external muscle membrane). Dalecki et al. found that the delivery of pulsed ultrasound to the frog heart in systole resulted in a reduction in the peak aortic pressure. Miyamoto et al. reported vasodilation of coronary arteries in canine studies by short term ultrasound therapy, with the magnitude of the dilation similar to that of intracoronary nitroglycerin. They speculated that the observed coronary vasodilation was a direct effect on vasomotor tone, and reported no temperature change to implicate a thermal effect. Suchkova et al., applied ultrasound to the surface of rabbit limb muscles following arterial ligation, and found that tissue perfusion was increased, accompanied by histologic evidence of dilated capillary beds. They further found this improvement in perfusion to be blocked by inhibition of nitric oxide synthase, implying that the mechanism of effect was dependent upon nitric oxide. Finally, animal studies have shown that ultrasound treatment can cause new myocardial tissue growth in conditions of chronic ischemia, and this is thought to be due to up-regulation of growth factor expression.
Thus, a number of underlying mechanisms have been proposed to explain why therapeutic ultrasound may have beneficial effects on cardiac function. It is possible that increased myocardial contractility, reduced aortic pressure, coronary vasodilation, and increased tissue perfusion occur by separate or related mechanisms. For example, the vasodilation may be secondary to the increased myocardial demand caused by increased contractility. Alternatively, a reduction in aortic pressure (afterload) may result in increased contractility. Increased tissue perfusion may be a manifestation of vasodilation at the capillary level.
While the exact mechanism(s) and sequence of events are not well understood, the beneficial effects of therapeutic ultrasound on cardiac function can be utilized to improve the care of patients with heart failure both chronically and during acute exacerbations. Long term improvement in heart failure treatment is possible with chronic intermittent ultrasound administration. Coronary artery disease is the underlying cause of HF in two-thirds of HF patients and coronary artery disease can lead to acute ischemic episodes, which can be treated by improving blood flow (reperfusion). Since ultrasound therapy can improve blood flow, therapeutic ultrasound can, thus, prevent HF. We have described the use of ultrasound in co-pending application Ser. No. 10/869,631, with methods and systems for leadless implantable devices that directly prevent and/or treat heart failure using ultrasound energy.
Second, the indications for permanent cardiac pacemaker implantation have greatly expanded to include the treatment of heart failure by pacing both the left and right ventricle, called cardiac resynchronization therapy (CRT) or bi-ventricular pacing. Randomized clinical trials have shown significant morbidity and mortality benefits with bi-ventricular pacing, especially when combined with an implantable cardioverter defibrillator (ICD). As described in co-pending application Ser. Nos. 11/315,023, and 11/315,524, a method of cardiac stimulation uses one or more implantable acoustic receiver-stimulators for cardiac stimulation, along with an implanted or externally-applied ultrasound controller-transmitter. Using this leadless system to avoid lead limitations and complications and gain other potential advantages as described in the co-pending applications, CRT therapy is applied to optimal single or multiple sites in the left or right heart and most notably endocardial left ventricular sites.
Third, another device therapy applying electrical current to the heart muscle is called Cardiac Contractility Modulation (CCM). These systems have some similarities to conventional cardiac pacemakers, in that they comprise a pulse generator implanted in the pectoral region of the chest and transvenous leads having electrodes in direct contact with heart tissue; in some cases, conventional pacemaker leads have been used in CCM therapy. However, in a conventional cardiac pacemaker, electrical current is delivered at sufficient amplitude and duration at a time in the cardiac cycle that will initiate a heart beat, known in the art as excitation. In contrast, for CCM therapy, electrical current is delivered during or immediately after a heart beat when the heart is unable to initiate another beat, known in the art as the absolute refractory period of the heart. The amplitude and duration of the electrical current would be sufficient for excitation, but since it is delivered in this refractory period it is thus considered non-excitatory. Instead of initiating a heat beat via excitation, the electrical field or electrical current delivered for CCM increases tissue contractility during the heart beat. As noted earlier, increased tissue contractility leads to improved cardiac function. It has been shown in basic investigational studies using this CCM approach that the action potential duration is prolonged during this non-excitatory electrical field delivery. It is thought that the underlying mechanism is an increase in calcium transport into the cells.
Early animal studies (Mohri et al.) employed two pairs of electrodes, one pair in the anterior LV wall and one pair in the posterior wall; each with approximately 3 cm inter-electrode distance. CCM non-excitatory electrical field delivery (20 mA biphasic square-waves of 30 ms duration) was delivered 30 ms after local R wave detection, between each electrode pair. An increase in contractility was found with either anterior or posterior delivery, but was greatest with simultaneous delivery to both the anterior and posterior pairs. The increase in contractility only occurred in the regions of electrical current delivery.
In acute human studies (Pappone et al.), CCM therapy was delivered either across two selected poles of an octapolar catheter in the coronary sinus (CS), on the epicardial aspect of the LV or on the RV septum from the tip electrode to the ring electrode of a commercially available active fixation pacing lead. The CCM current used was a biphasic, square-wave pulse 20-40 ms in duration, delivered 30-60 ms after detection of an electrical pulse using the local electrogram, with pulse amplitudes up to 14 mA. With LV delivery of 10 mA to the CS, some patients complained of chest discomfort. With RV septum delivery, 14 mA was able to be delivered without chest discomfort. Acute improvement in LV function was similar with LV or RV delivery; approximately a 9% increase in pressure gradient dP/dtmax and 10% increase in aortic pulse pressure.
One example of a CCM device is an Optimizer™ II (Impulse Dynamics, Israel). These have been implanted in patients and have been shown to improve cardiac function (Pappone et al., Stix et al.). This device employs one commercially available right atrial lead used for sensing only, and 2 commercially available transvenous bipolar active fixation leads implanted in the RV septum used for sensing a local electrogram and delivery of non-excitatory electrical current.
Because CCM devices use leads similar to cardiac pacemakers, they are subject to all the limitations and complications associated with currently available cardiac pacemakers. These lead issues have been extensively identified in our co-pending applications listed above. Additionally, although animal studies had shown greater efficacy with placement of the electrodes on the left ventricle, in clinical studies using coronary sinus leads for left ventricular non-excitatory CCM therapy, patients experienced chest pain, attributed to stimulation of the phrenic nerve. In the same patients, endocardial delivery to the right ventricular septum did not cause discomfort. It is likely, based on animal study results, that CCM therapy would be substantially improved using a system that enables endocardial left ventricular non-excitatory therapy.
Therefore, it would be desirable to provide a system without the need for transvenous leads, with the ability to optimally select sites on the endocardium, particularly in the left ventricle, and to select multiple sites for CCM delivery of non-excitatory electrical current.
Fourth, the concept of selective site pacing to initiate a preferred pattern of cardiac activation and/or mechanical contraction has been recently put forth to prevent heart failure in patients needing permanent pacing for bradycardia indications. Traditionally, the standard ventricular site for stimulation has been the RV apex for reasons of lead stability and ease of implantation. However, recent randomized clinical trials of patients requiring bradycardia pacing (DAVID and PAVE) have lead to the conclusion that the RV apex location is deleterious. The concept of selective site pacing has emerged, and has led to the reevaluation of all traditional pacing sites. New stimulation sites being evaluated require the use of non-passive fixation tips and more precise implant techniques. The ideal site(s) may be within the left ventricle in areas inaccessible using transvenous leads from within the coronary sinus. Selective site left ventricular or right ventricular stimulation alone may provide improved heart functioning or prevention of heart failure without the need for bi-ventricular stimulation. It would be desirable to provide selective site pacing with previously referred to leadless methods and systems using one or more implantable acoustic receiver-stimulators for cardiac stimulation, along with an implanted or externally-applied ultrasound controller-transmitter. The receiver-stimulator would be implanted in the left and/or right ventricle at one or more locations that initiate a preferred pattern of cardiac activation and/or mechanical contraction.
It would be desirable to treat patients who have had cardiac problems to prevent or delay them from becoming HF patients. It would be ideal to provide a single system to take advantage of the benefits of sonification, pacing and CCM and either based on user preference, pre-programmed therapy, or physiologic parameters that are measured, individual or combination treatments (sonication, pacing or CCM) could be provided.
Thus, it would further be desirable to provide an implantable device that combines the beneficial effects of direct application of ultrasound energy to cardiac tissue with the beneficial effects of a leadless electrical delivery device for cardiac resynchronization stimulation therapy, cardiac contractility modulation therapy, and/or selective site pacing therapy in order to improve cardiac function in heart failure patients or to prevent heart failure in other patients.
Other references include the following:
U.S. Pat. No. 4,651,716 Forester; George V. et al. Method and device for enhancement of cardiac contractility. U.S. Pat. No. 6,522,926 Kieval, et al.; Devices and methods for cardiovascular reflex control. U.S. Pat. No. 3,659,615, Enger; Encapsulated Non-Permeable Piezoelectric Powered Pacesetter, May 1972. U.S. Pat. No. 4,256,115, Bilitch; Leadless Cardiac Pacer, March 1981. U.S. Pat. No. 4,690,144, Rise et al; Wireless Transcutaneous Electrical Tissue Stimulator, September 1987. U.S. Pat. No. 5,170,784, Ramon et al; Leadless Magnetic Cardiac Pacemaker, December 1992. German Patent DE4330680 (abandoned), Zwicker; Device for Electrical Stimulation of Cells within a Living Human or Animal, March 1995. U.S. Pat. No. 5,405,367, Schulman et al; Structure and Method of Manufacture of an Implantable Micro stimulator, April 1995. U.S. Pat. No. 5,411,535, Fujii et al; Cardiac Pacemaker Using Wireless Transmission, May 1995. U.S. Pat. No. 5,749,909, Schroeppel et al; Transcutaneous Energy Coupling Using Piezoelectric Device, May 1998. U.S. Pat. No. 5,751,539, Stevenson et al; EMI Filter for Human Implantable Heart Defibrillators and Pacemakers, May 1998. U.S. Pat. No. 5,766,227, Nappholz et al; EMI Detection in an Implantable Pacemaker and the like, May 1998. U.S. Pat. No. 5,814,089, Stokes et al; Leadless Multisite Implantable Stimulus and Diagnostic System, September 1998. U.S. Pat. No. 5,817,130, Cox et al; Implantable Cardiac Cardioverter/Defibrillator with EMI Suppression Filter with Independent Ground Connection, October 1998. U.S. Pat. No. 5,978,204, Stevenson; Capacitor with Dual Element Electrode Plates, November 1999. U.S. Pat. No. 6,037,704, Welle; Ultrasonic Power Communication System, March 2000. U.S. Pat. No. 6,366,816, Marchesi; Electronic Stimulation Equipment with Wireless Satellite Units, April 2002. U.S. Patent Application Publication 2002/0077673, Penner et al; Systems and Methods for Communicating with Implantable Devices, June 2002. U.S. Pat. No. 6,424,234, Stevenson; Electromagnetic Interference (EMI) Filter and Process for Providing Electromagnetic Compatibility of an Electronic Device while in the Presence of an Electromagnetic Emitter Operating at the Same Frequency, July 2002. U.S. Pat. No. 6,445,953, Bulkes et al; Wireless Cardiac Pacing System with Vascular Electrode-Stents, September 2002. U.S. Pat. No. 6,654,638, Sweeney; Ultrasonically Activated Electrodes, November 2003. U.S. Patent Application Publication 2004/0172083, Penner; Acoustically Powered Implantable Stimulating Device, September 2004. WO9725098, Shlomo et al; Electrical Muscle Controller, July 1997. U.S. Pat. No. 6,725,093, Ben-Haim et al; Regulation of excitable tissue control of the heart based on physiological input, April 2004. U.S. Pat. No. 6,463,324, Ben-Haim et al; Cardiac output enhanced pacemaker, October 2002. U.S. Pat. No. 6,442,424, Ben-Haim et al. Local cardiac motion control using applied electrical signals, August 2002. U.S. Pat. No. 6,363,279, Ben-Haim et al; Electrical muscle controller, March 2002. U.S. Pat. No. 6,330,476, Ben-Haim et al; Electrical muscle controller using a non-excitatory electric field, December 2001. U.S. Pat. No. 6,317,631, Ben-Haim et al; Controlling heart performance using a non-excitatory electric field, November 2001. U.S. Pat. No. 6,298,268, Ben-Haim et al; Cardiac output controller, October 2001. U.S. Pat. No. 6,285,906, Ben-Haim et al; Muscle contraction assist device, September 2001. U.S. Pat. No. 6,236,887, Ben-Haim et al; Drug-device combination for controlling the contractility of muscles, May 2001. U.S. Pat. No. 6,233,484, Ben-Haim et al; Apparatus and method for controlling the contractility of muscles, May 2001. ACC/AHA Task Force on Practice Guidelines. Evaluation and Management of Chronic Heart Failure in the Adult. JACC 2002; 38:2101-13. Miyamoto T et al. Coronary Vasodilation by Noninvasive Transcutaneous Ultrasound An In Vivo Canine Study. Journal of the American College of Cardiology. 2003; 41:1623-7. McPherson D and Holland C. Seizing the Science of Ultrasound Beyond Imaging and Into Physiology and Therapeutics. Journal of the American College of Cardiology 2003; 41:1628-30. Forester G V, Roy O Z, and Mortimer A J. Enhancement of contractility in rat isolated papillary muscle with therapeutic ultrasound. Mol. Cell Cardiol. 1982; 14(8):475-7. Suchkova V N, et al. Ultrasound improves tissue perfusion in ischemic tissue through a nitric oxide-dependent mechanism. Throm Haemost. 2002; 88:865-70. Dalecki D. et al. Effects of pulsed ultrasound on the frog heart: I. Thresholds for changes in cardiac rhythm and aortic pressure. Ultrasound in Med & Biol. 1993; 19:385-390. Mortimer A J et al. Letter to the Editor: Altered Myocardial Contractility with Pulsed Ultrasound. Ultrasound in Med and Biol. 1987; 13(9):L567-9. Forester G V et al. Ultrasound Intensity and Contractile Characteristics of Rat Isolated Papillary Muscle. Ultrasound in Med. And Biol. 1985; 11(4):591-598. Meltzer R S, Schwarz K Q, et al. Therapeutic Cardiac Ultrasound. American Journal of Cardiology. 1991; 67:422-4. Kass D A, Chen C-H, Curry C, Talbot M, Berger R, Fetics B, Nevo E. Improved Left Ventricular Mechanics from Acute VDD Pacing in Patients with Dilated Cardiomyopathy and Ventricular Conduction Delay. Circulation 1999; 99:1567-73. Abraham W T, Fisher W G, Smith A L, Delurgio D B, Leon A R, Loh E, Kocovic D Z, Packer M, Clavell A L, Hayes D L, Ellestad M, Messenger J, for the MIRACLE study group. Cardiac Resynchronization in Chronic Heart Failure. N Engl J Med, 2002; 346:1845-53. Nishida T, et al. Extracorporeal cardiac shock wave therapy markedly ameliorates ischemia-induced myocardial dysfunction in pigs in vivo. Circulation. 2004; 110:3055-3061. Mohri S, et al. Cardiac contractility modulation by electric currents applied during the refractory period. Am J Physiol Heart Circ Physiol. 2002; 282:H1642-1647. Marrouche N F et al. Nonexcitatory stimulus delivery improves left ventricular function in hearts with left bundle branch block. J Cardiovasc Electrophysiol. 2002; 13:691-695. Mond H G, Gammage M D. Selective Site Pacing: The Future of Cardiac Pacing? PACE 2004; 27:835-836. Peschar M, et al. Left ventricular septal and apex pacing for optimal pump function in canine hearts. J Am Coll Cardiol 2003; 41:1218-1226. DAVID Trial Investigators. The Dual Chamber and VVI Implantable Defibrillator (DAVID) Trial. JAMA 2002; 288:3115-3123. Doshi, R N, et al. The Left Ventricular-Based Cardiac Stimulation Post AV Nodal Ablation Evaluation (PAVE) Study, oral presentation at American College of Cardiology, March 2004. Pappone C, et al. Cardiac Contractility Modulation by electric currents applied during the refractory period in patients with heart failure secondary to ischemic or idiopathic dilated cardiomyopathy. Am J Cardiol 2002; 90:1307-1313. Pappone C, et al. First human chronic experience with cardiac contractility modulation by nonexcitatory electrical currents for treating systolic heart failure: mid-term safety and efficacy results from a multicenter study. J Cardiovasc Electrophysiol 2004; 15:418-427. Stix G, et al. Chronic electrical stimulation during the absolute refractory period of the myocardium improves severe heart failure. European Heart J 2004; 25:650-655.